Dissolve yeast in warm water with 1 tsp brown sugar. Add oil, salt, and 4 cups (480 g) flour; mix, then knead in remaining flour until smooth and elastic (~10 minutes). Let rise covered until doubled.
Punch down; divide into 18 pieces. Roll each into a 15 cm (6 in) rope and form a ring, sealing ends.
Preheat oven to 190°C / 375°F. Bring 4 qt water + 2 tbsp brown sugar to a boil. Boil 4–5 bagels at a time: once they float, turn and boil 1 minute total.
Remove with slotted spoon to greased or parchment-lined tray. Bake 25–30 minutes until golden. Cool on rack.