Fort Peck is more than a fishing destination. The place is magical. More shoreline than the whole west coast. Wild country and more places to fish in a lifetime, plus you never know what is coming up the hole. Lakers, walleyes, sauger, saugeyes, pike, perch, burbot, salmon, bass, crappie, rainbows, browns...missed a few I am sure. Jigging, tip ups, spearing, soaking a minnow all great.
You then need to decide which part. The dam (Duck Creek to the Pines), Dry Arm, Hell Creek (my favorite) Crooked Creek all are wonderful but only the dam has reliable roads in winter.