diff --git a/pipes/WDL/tasks/tasks_interhost.wdl b/pipes/WDL/tasks/tasks_interhost.wdl
index bf4fb1b2c..38f64ad66 100644
--- a/pipes/WDL/tasks/tasks_interhost.wdl
+++ b/pipes/WDL/tasks/tasks_interhost.wdl
@@ -96,6 +96,9 @@ task multi_align_mafft {
 task beast {
   input {
     File    beauti_xml
+
+    Boolean beagle_double_precision=true
+    String? beagle_order
     
     String? accelerator_type
     Int?    accelerator_count
@@ -106,23 +109,60 @@ task beast {
     String  docker = "quay.io/broadinstitute/beast-beagle-cuda:1.10.5pre"
   }
 
-  Int disk_size = 300
-  Int boot_disk = 50
+  meta {
+    description: "Execute GPU-accelerated BEAST. For tips on performance, see https://beast.community/performance#gpu"
+  }
+  parameter_meta {
+    beagle_double_precision: {
+      description: "If beagle_double_precision=true, use double-precision calculation (perhaps set to false to gain execution speed if MCMC chain convergence is possible using single-precision calculation)."
+    }
+    beagle_order: {
+      description: "The order of CPU(0) and GPU(1+) resources used to process partitioned data."
+    }
+
+    accelerator_type: {
+      description: "[GCP] The model of GPU to use. For availability and pricing on GCP, see https://cloud.google.com/compute/gpus-pricing#gpus"
+    }
+    accelerator_count: {
+      description: "[GCP] The number of GPUs of the specified type to use."
+    }
+    gpu_type: {
+      description: "[Terra] The model of GPU to use. For availability and pricing on GCP, see https://support.terra.bio/hc/en-us/articles/4403006001947-Getting-started-with-GPUs-in-a-Cloud-Environment"
+    }
+    gpu_count: {
+      description: "[Terra] The number of GPUs of the specified type to use."
+    }
+  }
+
+  Int disk_size    = 300
+  Int boot_disk    = 50
   Int disk_size_az = disk_size + boot_disk
 
-  # TO DO: parameterize gpuType and gpuCount
+  # platform-agnostic number of GPUs we're actually using
+  Int gpu_count_used = select_first([accelerator_count, gpu_count, 1])
 
   command {
     set -e
     beast -beagle_info
     nvidia-smi
+
+    # if beagle_order is not specified by the user, 
+    # create an appropriate string based on the gpu count
+
+    default_beagle_order="$(seq -s, ~{gpu_count_used})"
+    beagle_order=~{default="$default_beagle_order" beagle_order}
+    echo "beagle_order: $beagle_order"
+
     bash -c "sleep 60; nvidia-smi" &
     beast \
       -beagle_multipartition off \
-      -beagle_GPU -beagle_cuda -beagle_SSE \
-      -beagle_double -beagle_scaling always \
-      -beagle_order 1,2,3,4 \
-      ${beauti_xml}
+      -beagle_GPU \
+      -beagle_cuda \
+      -beagle_SSE \
+      ~{true="-beagle_double" false="-beagle_single" beagle_double_precision} \
+      -beagle_scaling always \
+      ~{'-beagle_order ' + beagle_order} \
+      ~{beauti_xml}
   }
 
   output {
@@ -143,10 +183,10 @@ task beast {
     gpu:                 true                # dxWDL
     dx_timeout:          "40H"               # dxWDL
     dx_instance_type:    "mem1_ssd1_gpu2_x8" # dxWDL
-    acceleratorType:     select_first([accelerator_type, "nvidia-tesla-k80"])  # GCP PAPIv2
-    acceleratorCount:    select_first([accelerator_count, 4])  # GCP PAPIv2
-    gpuType:             select_first([gpu_type, "nvidia-tesla-k80"])  # Terra
-    gpuCount:            select_first([gpu_count, 4])  # Terra
+    acceleratorType:     select_first([accelerator_type, "nvidia-tesla-p4"])  # GCP PAPIv2
+    acceleratorCount:    select_first([accelerator_count, 1])  # GCP PAPIv2
+    gpuType:             select_first([gpu_type, "nvidia-tesla-p4"])  # Terra
+    gpuCount:            select_first([gpu_count, 1])  # Terra
     nvidiaDriverVersion: "410.79"
   }
 }