Scallops, shrimp, crab, clams, oysters, and mussels all change in recognizable ways when they are done. This guide gives the appearance cue the USDA chart uses for each group. It also covers the shell check for bivalves and the discard rule for shells that stay shut. For shrimp technique, see our shrimp grilling guide.
Scallops, shrimp, crab, and lobster: pearly and opaque
The USDA chart’s cue for shrimp, lobster, crab, and scallops is “Cook until flesh is pearly or white, and opaque.” The Arkansas extension sheet says shrimp and scallops “turn from fairly clear to cloudy when done.” It says lobster “turns red and the flesh becomes pearly.” Practical advice: cut one scallop in half to check the center, because the outside can look done before the middle has changed.
Clams, oysters, and mussels: the shell is the cue
The USDA chart gives the cue for clams, oysters, and mussels as “Cook until shells open during cooking.” The Arkansas sheet says oysters, clams, and mussels “open their shells when cooked.”
Practical advice: check the shells before they go on the grill, too. The Arkansas sheet says live shellfish may gape naturally but should close tightly when tapped, and shells that are not alive should be discarded.
Discard the shells that do not open
The Arkansas sheet says: “Discard any clams, mussels or oysters that do not open during cooking, since this could be a sign they were not heated thoroughly.” Practical advice: apply the same rule to grilled bivalves. The sheet also says: “If too many shells are cooking in the same pot, it’s … possible that the ones in the middle will not cook … thoroughly.” Practical advice: crowding applies to a grill basket too.
Fish has its own row
The USDA chart lists fish at “145 or cook until flesh is no longer translucent and separates easily with a fork.” This guide does not cover finfish. For finfish technique, see our guide to how to grill fish without it falling apart.
Keep raw and cooked seafood apart
The Arkansas sheet says: “when grilling outdoors, use separate plates for carrying raw product to the grill and taking the cooked product to the table.” Practical advice: set out a clean plate and tongs for the cooked shellfish before the first batch goes on.
Common mistakes and limits
- Practical advice: use the cue together with the shell check, not color alone.
- Practical advice: pull scallops when the center has just turned opaque.
- Practical advice: spread shells in one layer so each one heats.
- Practical advice: keep raw shellfish cold until it goes on the grill.
- Practical advice: use a grill basket for small shellfish, so they do not fall through the grates.
For the thermometer habit that carries over from meat, see our guide to grilling with a meat thermometer.
Sources
- USDA FSIS, Safe Minimum Internal Temperature Chart, checked 2026-10-08
- CDC, Safer Food Choices for Adults 65 Years or Older, checked 2026-10-08
- University of Arkansas Cooperative Extension, Safe Handling and Preparation of Fish and Shellfish Products (FSFCS100), checked 2026-10-08