Rinse halibut steaks or fillets with cold water and pat dry. Sprinkle both sides with salt and pepper and set aside.
Wash and prick potatoes and cook in a microwave oven on high for about 6-7 minutes or until fork tender. Wrap in foil or keep warm in oven.
Melt butter in a large frying pan. Add vegetables (onion, bell pepper, carrots and garlic) and sauté for 30-40 seconds.
Place halibut in pan and cook over medium-high heat until steaks are lightly browned on one side. Turn and cook other side until browned and fish flakes easily (takes 4-5 minutes per side). Turn heat to low and remove halibut steaks to a plate.
Add and stir the lemon juice and milk into the buttery vegetable sauce until heated through.
To serve: Slice red potatoes into 1/8-inch thick slices and divide among four plates. Place a halibut steak on top of the potatoes on each plate. Pour some of the buttery vegetable sauce from the pan over each steak and serve at once.